1. Technical Field
This disclosure relates generally to an injector assembly for a rocket engine and, more particularly, to an injector assembly having a pressure actuated valve.
2. Background Information
Certain modern rocket engines are adapted for deep throttling maneuvers in order to provide soft landings, orbital transfers, etc. The term “deep throttling” is used herein to describe a process of decreasing engine thrust from full throttle to generally less than thirty percent of full throttle.
Flow of liquid propellants, such as liquid hydrogen and liquid oxygen (also referred to as “LOX”), through an injector assembly into a combustion chamber is greatly decreased during a typical deep throttling maneuver. As the flow of the propellants decreases, the pressure exerted by the propellants in the injector assembly can begin to approach the pressure of combusted gases in the combustion chamber. The pressure differential between the propellants in the injector assembly and the combusted gases in the combustion chamber, therefore, can be relatively small when engine thrust is at substantially less than full throttle. If the pressure differential becomes small enough it can cause poor performance or poor combustion stability during deep throttling maneuvers. A small pressure differential, for example, can reduce atomization, vaporization and mixing of the propellants as they are injected into the combustion chamber. The flow of propellant into the combustion chamber can also be perturbed by low combustion chamber pressure perturbations, which can create additional combustion instability.
Certain rocket engines include a propellant injector assembly with a plurality of manifolds in order to maintain a sufficient pressure differential during deep throttling maneuvers. Such an injector assembly adjusts the quantity of propellant injected into the combustion chamber by switching between one or more of the manifolds, while maintaining propellant pressure in each manifold within a certain range. The flow of propellant into the combustion chamber therefore can be decreased without also substantially decreasing the pressure differential across the injector assembly. Each manifold, however, typically has a large internal volume that must be purged during, for example, low power operation of a primary booster. Such purging can disadvantageously create combustion instabilities caused by lower hydraulic stiffness of the injector assembly.